1. Field of the Invention
The present invention relates, in general, to a method of controlling the shifting of gears in a hybrid vehicle that is of a type of transmission mounted electric device (TMED) using an automatic transmission or a double clutch transmission (DCT), such that a power-on upshift operation can be carried out simultaneously when the driving mode of the hybrid vehicle is converted from an electric vehicle (EV) mode to a hybrid-electric vehicle (HEV) mode.
2. Description of Related Art
Generally, transmission mounted electric device (TMED)-type hybrid vehicles have an engine clutch for power-connection between an engine and a motor, and, when converted from electric vehicle (EV) driving mode to hybrid-electric vehicle (HEV) driving mode, should start the engine and engage the engine clutch such that power from the engine is transmitted to the transmission.
In such a TMED-type hybrid vehicle having the engine clutch, when a driver depresses an acceleration pedal so as to perform an upshift operation (i.e. power-on upshifting operation) while the driving mode of the hybrid vehicle is converted from the EV driving mode to the HEV driving mode, according to the related art, the EV-HEV conversion and the power-on upshifting operation are sequentially carried out in the order named or reversely due to complexity of control.
FIG. 1 is a graph showing a relationship of rpms of the engine and the motor over time when the engine clutch is first engaged and then the shift operation is performed, in the case where engagement of the engine clutch and the shift operation are required at the same time. In the graph, when upshifting to a high gear as a target gear is set after the engine starts in response to an engine-on signal is generated, a shift-prevention BIT to prevent shift operation is activated until the engine clutch is engaged and locked up, since the engine clutch is not yet engaged, and then when the shift-prevention bit is deactivated, the actual shift-performing bit to perform an actual shift operation is activated to complete the shift operation.
Although the above-mentioned control method can avoid complexity of control with separate implementation of engagement of the engine clutch from the shift operation, the shift operation is carried out after the engagement of the engine clutch and thus is delayed, so that an increase in torque of driving wheels is also delayed, reducing the acceleration performance of a vehicle. In addition, such a time lag to start the shift operation may cause poor performance in terms of noise, vibration, and harshness (NVH) of a vehicle.
In the meantime, FIG. 2 is a graph showing a relationship of rpms of the engine and the motor over time when shift operation is first carried out and then engagement of the engine clutch is performed, in the case where the engagement of the engine clutch and the shift operation are required at the same time. In the graph, when the engine starts in response to an engine-on signal generated after upshift to high gear as a target gear is set, the shift operation is first performed such that actual shift-performing bit is first activated while deactivating shift-prevention bit, and then when the actual shift-performing bit is deactivated by the completion of the shift operation, the engine clutch is engaged locked up.
Although the above-mentioned control method first performs the shift operation so that an increase in torque of driving wheels of a vehicle can be performed quickly, a maximum torque for rpms of the motor is limited, so a desired torque can be provided to the driving wheels, provided that the engine clutch is engaged. Thus, a difference in torque of driving wheels occurs due to the process of the shift operation and the engagement of the engine clutch, degrading linear acceleration performance. In addition, like in the former case of shifting after the engagement of the engine clutch, a time lag to accelerate a vehicle occurs, and the engine is unnecessarily operated during the shift operation, degrading fuel efficiency.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.